Hydro Cannon and Water Shuriken dramatically improve Greninja as a viable glass cannon for Great and Ultra League, especially themed cups. Water Shuriken is currently the highest energy-generating Fast Move and allows Greninja to reach Hydro Cannon at incredible speed, even faster than Swampert. Combined with the 35-energy move Night Slash, Greninja has one of fastest movesets in the game. That said, Greninja is unlikely to unseat Swampert in the open leagues because of its worse weakness profile, so it may see more action in themed cups.

Greninja's playstyle is comparable to Shiftry's, another Dark type with similar energy generation and spammy Charged Moves. Like Shiftry, Greninja has low stat product. It needs shields to stay in the fight and is vulnerable to any kind of Fast Move pressure. Greninja thrives best with energy advantage and in Charged Move-oriented matchups where it can command the pace.

Greninja stands out most in Ultra League where it has more bulk to work with and common targets like Charizard, Giratina, Jellicent, and Cresselia. It's susceptible to being walled by several Pokemon, including Water/Fairies like Azumarill or Tapu Fini, Fighting types like Poliwrath or Virizion, and Dark/Dragons like Zweilous or Guzzlord in themed cups that include Dark types.

No, Water Shuriken will become a permanent addition to Greninja's movepool at the start of the event and won't require an Elite TM.